Internal Bone Fixation System with Integrated Mixer

ABSTRACT

Systems and methods for repairing a weakened or fractured bone are disclosed herein. A system for repairing a fractured bone includes a delivery catheter having an elongated shaft with a proximal end, a distal end, and a longitudinal axis therebetween, wherein the delivery catheter has an inner void for passage of bone cement components and an inner lumen for passage of a mixing element; an internal bone fixation device releasably engaging the distal end of the delivery catheter, wherein the internal bone fixation device moves from a first compact state to a second expanded state when the bone cement components are delivered to the internal bone fixation device and mixed within the internal bone fixation device; and a spinning mechanism engaged to a rotatable shaft, wherein the spinning mechanism is inserted into the internal bone fixation device.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/016,641, filed on Jan. 18, 2008, the entirety of this application ishereby incorporated herein by reference for the teachings therein.

FIELD

The embodiments disclosed herein relate to systems for repairing aweakened or fractured bone, and more particularly to systems thatinclude internal bone fixation devices having bone cement componentsthat are mixed together and cured within the internal bone fixationdevice in situ and methods of using these systems for repairing aweakened or fractured bone.

BACKGROUND

Fracture repair is the process of rejoining and realigning broken bones.Fracture repair is required when there is a need for restoration of thenormal position and function of the broken bone. Throughout the stagesof fracture healing, the bones must be held firmly in the correctposition and supported until it is strong enough to bear weight. In theevent the fracture is not properly repaired, malalignment of the bonemay occur, resulting in possible physical dysfunction of the bone orjoint of that region of the body.

The addition of bone cements or other compounds to a fractured bone forrepairing bone and, for example, joining bones are known in the art andtypically requires at least two steps. Conventional bone cementinjection devices are similar to a household caulking gun. Typically,the injection device has a pistol-shaped body, which supports acartridge containing the bone cement. Bone cements are usually found astwo component systems (powder and liquid) and must be mixed in a mixerand transferred into the cartridge for injection. In conventional bonecement mixers, the mixing element or stirrer is inserted into the mixingvessel after the bone cement powder and monomer liquid have been placedin the vessel. When mixing is complete, the stirrer is withdrawn fromthe cement and the cement is manually transferred from the mixing vesselto the injection device. Stirrer withdrawal from the cement exposes alarge surface area of the cement to room air and undesirably introducessignificant amounts of monomer liquid vapor in the ambient air. Thisprocess is unpleasant for individuals mixing the cement, since the mixedcement often contains an offensive, noxious odor. Furthermore, removalof the mixed cement from the mixing vessel into the cartridge of theinjection device is cumbersome, time consuming, and has the potentialfor being mishandled and/or dropped.

Once the bone cement has been added to the cartridge of the injectiondevice, the bone cement is delivered to the site of the bone fracture.Because the bone cement may be quite thick and viscous, delivering thebone cement from the injection device often requires a great deal ofeffort applied to the device plunger. Thus, both strength and dexterityare required on the part of the medical professional performing theprocedure. The bone cement itself may cause complications including theleakage of the bone cement to an area outside of the fractured bonesite, which can result in soft tissue damage as well as nerve root painand compression. Other reported complications include pulmonaryembolism, respiratory and cardiac failure, and death.

Thus, there is a need in the art for devices that can be used to repaira weakened or fractured bone in an effective, efficient and safe manner.

SUMMARY

Systems and methods for repairing a weakened or fractured bone aredisclosed herein. According to aspects illustrated herein, there isprovided a system for repairing a fractured bone that includes adelivery catheter having an elongated shaft with a proximal end, adistal end, and a longitudinal axis therebetween, wherein the deliverycatheter has an inner void for passage of bone cement components and aninner lumen for passage of a mixing element; an internal bone fixationdevice releasably engaging the distal end of the delivery catheter,wherein the internal bone fixation device moves from a first compactstate to a second expanded state when the bone cement components aredelivered to the internal bone fixation device and mixed within theinternal bone fixation device; and a spinning mechanism engaged to arotatable shaft, wherein the spinning mechanism is inserted into theinternal bone fixation device.

According to aspects illustrated herein, there is provided a method forrepairing a fractured bone that includes gaining access to an innercavity of the fractured bone; providing a system for use in repairingthe fractured bone, the system comprising an internal bone fixationdevice releasably engaging a delivery catheter, the internal bonefixation device housing a powder component of a bone cement; positioningthe internal bone fixation device spanning at least two bone segments ofthe fractured bone; adding a liquid component of the bone cement to theinternal bone fixation device by passage through an inner void of thedevice; inserting the mixing element through the delivery catheter andinto the internal bone fixation device; activating the mixing element tomix the powder component and the liquid component of the bone cementwithin the internal bone fixation device, wherein the internal bonefixation device moves from a first compact state to a second expandedstate; removing the mixing element from the device; waiting for themixed bone cement to cure, wherein the curing of the bone cement resultsin a hardened internal bone fixation device; and releasing the hardenedinternal bone fixation device from the delivery catheter.

According to aspects illustrated herein, there is provided a method forrepairing a fractured bone that includes gaining access to an innercavity of the fractured bone; providing a system for use in repairingthe fractured bone, the system comprising an internal bone fixationdevice releasably engaging a delivery catheter, the internal bonefixation device housing a powder component of a bone cement; positioningthe internal bone fixation device spanning at least two bone segments ofthe fractured bone; adding a liquid component of the bone cement to theinternal bone fixation device by passage through an inner void of thedevice; inserting a mixing element through the delivery catheter andinto the internal bone fixation device, the mixing element comprising aspinning mechanism releasably engaging a rotatable shaft; activating themixing element to mix the powder component and the liquid component ofthe bone cement within the internal bone fixation device, wherein theinternal bone fixation device moves from a first compact state to asecond expanded state; releasing the spinning mechanism from therotatable shaft; removing the rotatable shaft from the device; waitingfor the mixed bone cement to cure, wherein the curing of the bone cementresults in a hardened rebar-enforced internal bone fixation device; andreleasing the hardened rebar-enforced internal bone fixation device fromthe delivery catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently disclosed embodiments will be further explained withreference to the attached drawings, wherein like structures are referredto by like numerals throughout the several views. The drawings shown arenot necessarily to scale, with emphasis instead generally being placedupon illustrating the principles of the presently disclosed embodiments.

FIG. 1 shows a perspective view of a system for repairing a weakened orfractured bone of the presently disclosed embodiments.

FIG. 2 shows a perspective view of a system for repairing a weakened orfractured bone of the presently disclosed embodiments.

FIG. 3A and FIG. 3B show close-up views of some of the main componentsof a system for repairing a weakened or fractured bone of the presentlydisclosed embodiments. FIG. 3A shows a perspective view of a distal endof the system. FIG. 3B shows a cross-sectional view of the system takenalong line B-B of FIG. 3A.

FIG. 4 shows a perspective view of a mixing element of a system forrepairing a weakened or fractured bone of the presently disclosedembodiments.

FIG. 5 shows close-up views of a distal end of a system for repairing aweakened or fractured bone of the presently disclosed embodiments. Thevarious method steps showing an exemplary embodiment of a two-componentbone cement being mixed within an expandable body in situ, are shown inFIG. 5A-D.

FIG. 6A and FIG. 6B show some of the method steps for utilizing a systemof the presently disclosed embodiments for repair of a weakened orfractured bone. FIG. 6A shows an expandable body in a compact state.FIG. 6B shows the expandable body in an expanded state, after atwo-component bone cement has been added, mixed and hardened in situ.

While the above-identified drawings set forth presently disclosedembodiments, other embodiments are also contemplated, as noted in thediscussion. This disclosure presents illustrative embodiments by way ofrepresentation and not limitation. Numerous other modifications andembodiments can be devised by those skilled in the art which fall withinthe scope and spirit of the principles of the presently disclosedembodiments.

DETAILED DESCRIPTION

Systems and methods for repairing weakened or fractured bones aredisclosed herein. The systems disclosed herein include an internal bonefixation device that is an expandable body. A powder component of a bonecement is contained within the expandable body. During a procedure forrepairing a fractured bone, an internal bone fixation device of thesystem is placed within an inner cavity of a fractured bone. Once inplace, a liquid component of the bone cement is added to thepowder-filled internal bone fixation device. A mixing element is thenpassed through an inner lumen of a delivery catheter that is engaged tothe internal bone fixation device. The two components of the bone cementare uniformly mixed in the internal bone fixation device in situ. Thefully mixed bone cement subsequently goes through a curing cycle and ishardened within the internal bone fixation device. The hardened internalbone fixation device may then be released from the delivery catheter andsealed to enclose the cured bone cement within the internal bonefixation device. The hardened internal bone fixation device remainswithin the inner cavity of the fractured bone and provides support andproper orientation of the fractured bone resulting in the repair,healing, and strengthening of the fractured bone. The systems forrepairing a weakened or fractured bone disclosed herein provide manyadvantages over known systems including, but not limited to, minimizingthe amount of air bubbles in the mixed bone cement, minimizing therelease of monomer liquid vapor to the air, reducing the cumbersome stepof moving the bone cement from a mixer to an injection device, avoidingthe difficulties encountered when trying to push a fully mixed bonecement through an injection device, and minimizing the amount of bonecement that leaks out to surrounding bone and tissues.

In an embodiment, a two-component bone cement is a powder/liquid systembased on a polyacrylic cement (a polymethacrylic cement) or a calciumphosphate cement (CPC). In an embodiment, the two-component bone cementis PolyMethylMethAcrylate (PMMA). PMMA is supplied as apolymethylmethacrylate (PMMA) powder and a liquid methyl methacrylate(MMA). When mixed these yield a dough-like cement that graduallyhardens. In an embodiment, the PMMA bone cement is a non-absorbable bonecement, such as Surgical Simplex P, Palacos® R, Zimmer Regular, ZimmerLow Viscosity (LVC), CMW-I, CMW-3, Osteopal®, Osteobond®, Endurance™bone cement, or a similar product. In an embodiment, the bone cement maybe a non-absorbable PMMA bone cement with antibiotics, such as Palacos®R with gentamycin, Surgical Simplex P with tobramycin, or a similarproduct. The bone cement may be an absorbable product, such as NorianSRS®, calcium phosphate cement (CPC), calcium phosphate hydraulic cement(CPHC), sodium citrate modified calcium phosphate cement, hydroxyapatite(HA) cement, hydroxyapatite calcium phosphate cements (CPCs); abeta-TCP-MCPM-CSH cement [beta-tricalcium phosphate (beta-TCP),monocalcium phosphate monohydrate (MCPM), and calcium sulfatehemihydrate (CSH)]; a bioactive bone cement (GBC) with bioactiveMgO—CaO—SiO2-P2O5-CaF2 glass beads and high-molecular-weight polymethylmethacrylate (hPMMA); a tricalcium phosphate (TCP), tetracalciumphosphate (TTCP), and dicalcium phosphate dehydrate (DCPD) bone cementwith dense TCP granules; an hPMMA with delta- or alpha-alumina powder(delta-APC or alpha-APC); a similar product; or any other material thatprovides sufficient strength upon hardening. In an embodiment, thetwo-component bone cement is a calcium phosphate two component apatiticcement composition. In an embodiment, the two-component bone cement is apolyurethane material. Those skilled in the art will recognize that themixing element and delivery catheter of the presently disclosedembodiments are compatible with all types of bone cement. Furthermore,the devices of the presently disclosed embodiments are equally effectivewith all viscosity bone cements, thereby enabling a single device to beemployed for any bone cement, ranging from low viscosity cements to highviscosity cements. In addition, vacuum may be used, if desired, therebyfurther expanding the range of products with which the devices may beemployed.

Several epoxies known in the art are suitable for use as bone cementsand vary in viscosity, cure times, and hardness (durometer or shore)when fully cured. A durometer of a material indicates the hardness ofthe material, defined as the material's resistance to permanentindentation. Depending on the amount of resultant support that isnecessary for a given bone fracture, a specific durometer bone cementmay be chosen. The durometer of a material may be altered to achieveeither greater rigidity or a more malleable result. The mechanicalproperties of the bone cement may dictate using methods/measures thatare typical for high-strength and high-impact materials including butnot limited to, tensile strength and tensile modulus, tensile strengthtests, ultimate modulus, Poisson's ratio, hardness measurements likeVickers and Charpy Impact which measures yield strength and toughness.

A system disclosed herein may be used for the repair of bones that haveweakened or fractured due to any of the bone diseases including, but notlimited to osteoporosis, achondroplasia, bone cancer, fibrodysplasiaossificans progressiva, fibrous dysplasia, legg calve perthes disease,myeloma, osteogenesis imperfecta, osteomyelitis, osteopenia,osteoporosis, Paget's disease, scoliosis, and other similar diseases. Asystem disclosed herein may be used for the repair of bones that haveweakened or fractured due to an injury, for example, a fall. A devicedisclosed herein may be used during a percutaneous vertebroplasty orkyphoplasty procedure.

The main components of a system 100 for repairing a weakened orfractured bone are shown generally in FIG. 1 in conjunction with FIG. 2.The system 100 includes a delivery catheter 110 having an elongatedshaft with a proximal end 102, a distal end 104, and a longitudinal axistherebetween. In an embodiment, the delivery catheter 110 has a diameterof about 3 mm. The distal end 104 of the delivery catheter 110terminates in an expandable body 103. The expandable body 103 is madefrom a pliable, resilient, conformable, biocompatible, and strongmaterial. The expandable body 103 may be referred to as an internal bonefixation device (IBFD). As shown in FIG. 1 the expandable body 103comprises a powder component 122 of a two-component bone cement. Theexpandable body 103 is able to move from a first compact position to asecond expanded position when a liquid component of the two-componentbone cement is delivered to the expandable body 103. In an embodiment,the expandable body 103 has a compact diameter of about 2.5 mm. In anembodiment, the expandable body 103 has an expanded diameter rangingfrom about 4 mm to about 9 mm. The powder and/or liquid components ofthe two-component bone cement may be delivered to the expandable body103 via an inner void capable of allowing the components to passthrough. The powder component 122 of the bone cement may be pre-loadedin the expandable body 103 or may be added to the expandable body 103 byinjection, suction (using a vacuum) or other methods known in the art.

The expandable body 103 may be round, flat, cylindrical, oval,rectangular or another shape. The expandable body 103 may be formed froma material, including but not limited to, urethane, polyethyleneterephthalate (PET), nylon elastomer and other similar polymers. In anembodiment, the expandable body 103 is constructed out of a PET nylonaramet or other non-consumable materials. PET is a thermoplastic polymerresin of the polyester family that is used in synthetic fibers.Depending on its processing and thermal history, PET may exist both asan amorphous and as a semi-crystalline material. Semi-crystalline PEThas good strength, ductility, stiffness and hardness. Amorphous PET hasbetter ductility, but less stiffness and hardness. PET can be semi-rigidto rigid, depending on its thickness, and is very lightweight. PET isstrong and impact-resistant, naturally colorless and transparent and hasgood resistance to mineral oils, solvents and acids.

In an embodiment, the expandable body 103 is designed to evenly contactan inner wall of a cavity in a fractured bone. In an embodiment, theexpandable body 103 may have a pre-defined shape to fit inside thecavity in a particularly shaped bone. For example, as depicted in theembodiment of FIG. 1, the pre-defined shape of the expandable body 103may be an elongated cylinder. The expandable body 103 has an outersurface 125. In an embodiment, the outer surface 125 of the expandablebody 103 is substantially even and smooth and substantially mates with awall of the cavity in the bone. In an embodiment, the outer surface 125of the expandable body 103 is not entirely smooth and may have somesmall bumps or convexity/concavity along the length. In someembodiments, there are no major protuberances jutting out from the outersurface 125 of the expandable body 103. The expandable body 103 may bedesigned to remain within the cavity of the bone and not protrudethrough any holes or cracks in the bone. In an embodiment, the outersurface 125 of the expandable body 103 may be flush with the wall of thecavity and when the expandable body 103 is expanded, the outer surface125 may contact the wall of the cavity along at least a portion of thesurface area. In an embodiment, when the expandable body 103 isexpanded, a majority or all of the body's 103 outer surface 125 does notcontact the wall of the cavity and does not extend through any holes orcracks in the bone.

The outer surface 125 of the expandable body 103 may be coated withmaterials such as drugs, bone glue, proteins, growth factors,antibiotics, or other coatings. For example, after a minimally invasivesurgical procedure an infection may develop in a patient, requiring thepatient to undergo antibiotic treatment. An antibiotic drug may be addedto the outer surface 125 of the expandable body 103 to prevent or combata possible infection. Proteins, such as, for example, the bonemorphogenic protein or other growth factors have been shown to inducethe formation of cartilage and bone. A growth factor may be added to theouter surface 125 of the expandable body 103 to help induce theformation of new bone. Due to the lack of thermal egress of the bonecement in the expandable body 103, the effectiveness and stability ofthe coating is maintained.

In an embodiment, the outer surface 125 of the expandable body 103 mayhave ribs, ridges, bumps or other shapes to help the expandable body 103conform to the shape of a bone cavity. The expandable body 103 may beconstructed to achieve transit within luminal cavities of bones and toexpand, manipulate, and remove obstructions. In this way, the expandablebody 103 may slide easier within the luminal bodies without coming incontact with surrounding tissue. The expandable body 103 may also bedesigned to be placed in a bone and to grab a fractured bone without anyslippage using a textured surface with a variety of shapes such as smallridges or ribs.

In an embodiment, a water soluble glue is applied to the outer surface125 of the expandable body 103. When the expandable body 103 is expandedand engages a moist bone, the water soluble glue on the outer surface125 of the expandable body 103 becomes sticky or tacky and acts as agripping member to increase the conformal bond of the expandable body103 to the bone. Once the expandable body 103 is expanded, the outersurface 125 of the expandable body 103 grips the bone forming amechanical bond as well as a chemical bond. These bonds prevent thepotential for a bone slippage. The water soluble glue may be cured byany light (e.g., UV not required).

In an embodiment, the expandable body 103 has a textured surface whichprovides one or more ridges that allow grabbing all portions of bonefragments of a fractured bone. In an embodiment, ridges arecircumferential to the expandable body 103 and designed to add more grabto the inflated expandable body 103 on contact with the fractured bone.The ridges are also compressive so the ridges fold up on the fracturedbone when the expandable body 103 is completely inflated. In anembodiment, sand blasted surfacing on the outer surface 125 of theexpandable body 103 improves the connection and adhesion between theouter surface 125 of the expandable body 103 and the inner bone. Thesurfacing significantly increases the amount of surface area that comesin contact with the bone resulting in a stronger grip.

The expandable body 103 of the system 100 typically does not have anyvalves. One benefit of having no valves is that the expandable body 103may be inflated or deflated as much as necessary to assist in thefracture reduction and placement. Another benefit of the expandable body103 having no valves is the efficacy and safety of the system 100. Sincethere is no communication passage of bone cement to the body therecannot be any leakage of the bone cement because all the cement iscontained within the expandable body 103. In an embodiment, a permanentseal is created between the expandable body 103 that is both hardenedand affixed prior to the delivery catheter 110 being removed. Theexpandable body 103 may have valves, as all of the embodiments are notintended to be limited in this manner.

The expandable body 103 of the system 100 has a diameter ranging fromabout 5 mm to about 9 mm. The expandable body 103 of the system 100 hasa length ranging from about 20 mm to about 80 mm. In an embodiment, theexpandable body 103 has a diameter of about 5 mm and a length of about30 mm. In an embodiment, expandable body 103 has a diameter of about 5mm and a length of about 40 mm. In an embodiment, the expandable body103 has a diameter of about 6 mm and a length of about 30 mm. In anembodiment, the expandable body 103 has a diameter of about 6 mm and alength of about 40 mm. In an embodiment, the expandable body 103 has adiameter of about 6 mm and a length of about 50 mm. In an embodiment,the expandable body 103 has a diameter of about 7 mm and a length ofabout 30 mm. In an embodiment, the expandable body 103 has a diameter ofabout 7 mm and a length of about 40 mm. In an embodiment, the expandablebody 103 has a diameter of about 7 mm and a length of about 50 mm.

In an embodiment, a stiffening member 105 surrounds the elongated shaftof the delivery catheter 110 and provides rigidity over the elongatedshaft 101. In an embodiment, a pusher or stabilizer 116 is loadedproximal to the expandable body 103. In an embodiment, a slip sleeve 107surrounds the stiffening member 105. In an embodiment, the slip sleeve107 surrounds the stiffening member 105 from the proximal end 123 of theexpandable body 103 up until the pusher 116. One or more radiopaquemarkers or bands 130 may be placed at various locations along theexpandable body 103 and/or the slip sleeve 107. A radiopaque ink bead133 may be placed at the distal end 121 of the expandable body 103 foralignment of the system 100 during fluoroscopy. The one or moreradiopaque bands 130, using radiopaque materials such as barium sulfate,tantalum, or other materials known to increase radiopacity, allows amedical professional to view the system 100 using fluoroscopytechniques. The one or more radiopaque bands 130 also provide visibilityduring inflation of the expandable body 103 to determine the precisepositioning of the expandable body 103 and the system 100 duringplacement and inflation. The one or more radiopaque bands 130 permitvisualization of any voids that may be created by air that getsentrapped in the expandable body 103. The one or more radiopaque bands130 permit visualization to preclude the expandable body 103 frommisengaging or not meeting the bone due to improper inflation tomaintain a uniform member/bone interface.

In an embodiment, an adapter 115, such as a Tuohy-Borst adapter, engagesthe proximal end 102 of the delivery catheter 110. A mixing element 150may be introduced into one of the side-arms of the adapter 115 andpasses within an inner lumen of the delivery catheter 110 up until thedistal end 104 of the delivery catheter 110. The mixing element 150 ismovable within the expandable body 103. The mixing element 150 mixes thepowder and liquid components of the bone cement together in situ to forma flowable bone cement. A bone cement injection system 160 housing thepowder and/or the liquid components of the bone cement may be introducedinto another side-arm of the adapter 115. Alternately, a Luer fittingmay engage the proximal end 102 of the delivery catheter 110 and a Luerfitting would exist on the mixing element 150 such that the deliverycatheter 110 and the mixing element 150 would lock together.

Examples of bone cement injection systems 160 include, but are notlimited to, caulking gun type systems and syringe systems. In theembodiment shown in FIG. 2, the bone cement injection system is asyringe 160. In an embodiment, the syringe 160 has a control mechanismthat regulates the flow of the liquid component. The control mechanismof the syringe 160 allows the liquid component to flow into the deliverycatheter 110 and the flow may be stopped if desired. The syringe 160makes direct contact to control the directional flow of the liquidcomponent, and the direction of flow of the liquid componentinstantaneously changes within the delivery catheter 110 in response toa change in the direction of the syringe 160. The liquid component has aviscosity as measured in Centipoise (cP), the unit of dynamic viscosity,so the liquid component may be infused from the syringe 160 into thedelivery catheter 110 and into the expandable body 103.

In an embodiment, a separation area is located at the junction betweenthe distal end 123 of the expandable body 103 and the elongated shaft ofthe delivery catheter 110. The separation area may have a stressconcentrator. The stress concentrator may be a notch, groove, channel orsimilar structure that concentrates stress in the separation area. Thestress concentrator of the separation area may be notched, scored,indented, pre-weakened or pre-stressed to direct separation of theexpandable body 103 from the elongated shaft of the delivery catheter110 under specific torsional load. The separation area ensures thatthere are no leaks of the bone cement from the elongated shaft of thedelivery catheter and/or the expandable body. The separation area sealsthe expandable body and removes the elongated shaft of the deliverycatheter by making a break at a known or predetermined site (e.g., aseparation area). The separation area may be various lengths and up toabout an inch long. In an embodiment, when torque (twisting) is appliedto the delivery catheter 110, the elongated shaft 101 separates from theexpandable body 103. The twisting creates a sufficient shear to breakthe residual bone cement and create a clean separation of the body/shaftinterface. In an embodiment, the expandable body 103 is cut from thedelivery catheter 110 using a cutting device.

FIG. 3A and FIG. 3B show close-up views of some of the main componentsof the system 100. As shown in FIG. 3A, one or more radiopaque markersor bands 130 are placed at various locations along the slip sleeve 107of the system 100. Those skilled in the art will recognize thatradiopaque markers 130 may also be placed at various locations along theexpandable body 103. In an embodiment, the one or more radiopaque bands130 are placed at intervals of about 10 mm along the length of the slipsleeve 107. In an embodiment, a radiopaque ink bead 133 is placed at thedistal end 121 of the expandable body 103 for easy visualization andalignment of the system 100 by fluoroscopy during a repair procedure.The radiopaque markers 130 and radiopaque ink bead 133 are formed usingradiopaque material such as barium sulfate, tantalum, or other materialsknown to increase radiopacity. The radiopaque markers 130 providevisibility during inflation of the expandable body 103 to determine theprecise positioning of the expandable body 103 and the delivery catheter110 during placement and inflation. The radiopaque markers 130 permitvisualization of voids created by air that may be entrapped in theexpandable body 103. The radiopaque markers 130 permit visualization topreclude the expandable body 103 from misengaging or not meeting thesurface of a bone due to improper inflation. Once the correctpositioning of the expandable body 103 and delivery catheter 110 aredetermined, the proximal end of the delivery catheter 110 may beattached to a delivery system that contains a bone cement.

A cross-sectional view taken along line B-B of FIG. 3A is shown in FIG.3B. For simplicity, the mixing element 150 has not been shown. As shownin FIG. 3B, the stiffening member 105 surrounds and provides rigidity tothe elongated shaft of the delivery catheter 110. The outer slip sleeve107 has not been shown in this figure. The mixing element conduit 111provides a space for the mixing element 150 to pass through. The innervoid 113 for passage of the bone cement components is formed between theouter surface 117 of the mixing element conduit 111 and the innersurface 124 of the delivery catheter 110. The outer surface 117 of themixing element conduit 111 allows for a separation between the mixingelement and the bone cement components within the elongated shaft 101 ofthe deliver catheter 110.

FIG. 4 in conjunction with FIG. 2 shows a mixing element 150 for usewith the system 100 of the presently disclosed embodiments. The mixingelement 150 is used to mix the two-component bone cement within theexpandable body 103 in situ. The mixing element 150 includes a handle151 attached to a rotatable shaft 152 that terminates in a spinningmechanism 154. The spinning mechanism 154 may be disposable ordesignated for single-use only. The spinning mechanism 154 may comprisea wire, a fin, a plug, a burr, a blade or any other spinner known in theart. The shape of the spinning mechanism 154 may include a propeller, anegg beater, a sinusoidal wire or any other shape known in the art. Thespinning mechanism 154 may be any shape and size, depending upon theparticular use and the size and shape of the IBFD 100 to be used. Forvarious uses, the shape may be ovoid, spherical, ellipsoidal,cylindrical, cubical, prismatic, spool-shaped, bell-shaped, acombination of these shapes, or an amorphous shape. The spinningmechanism 154 mixes the components of the bone cement in the expandablebody 103 in situ until a certain viscosity is reached. For example, ifthe spinning mechanism 154 is a propeller, a sensor on the propeller canmonitor the drag on the propeller and determine when a certain viscosityhas been reached and the pressure is maintained in the expandable body103. The rotatable shaft 152 may be attached to a drive mechanismincluding, but not limited to, an electric motor, battery powered,pneumatic or other power source engaged to the handle 151. If the drivemechanism is a motor, a sensor on the motor can monitor the drag on thespinning mechanism 154 and determine when a certain viscosity has beenreached and the pressure is maintained in the expandable body 103. Themixing element 150 may be set to stir the two-component bone cement fora predetermined time or until a certain viscosity is reached, which willcause the propeller to stop. In an embodiment, the mixing of the bonecement occurs under vacuum.

In certain situations, it is desirable to use a mixing element 150 thatincludes a handle 151 attached to a rotatable shaft 152 that terminatesin a releasable spinning mechanism 154. The spinning mechanism 154 maybe disengaged from the rotatable shaft 152 by various techniquesincluding, but not limited to, the presence of a stress concentrator ata separation area on the mixing element 150, by use of an active releasemechanism or by unscrewing the rotatable shaft 152 from the spinningmechanism 154. Other means of removing the spinning mechanism 154 fromthe rotatable shaft 152 are envisioned and fall within the scope andspirit of the presently disclosed embodiments. If the spinning mechanism154 is disengaged from the mixing element 150 and remains within theIBFD 100 during healing, the combination of the expandable body 103, thehardened bone cement, and the spinning mechanism 154, function as arebar-enforced IBFD and provide extra strength and support to thefractured bone during the healing process.

In an embodiment, a separation area 153 is located at the junctionbetween a distal end of the rotatable shaft 152 and a proximal end ofthe spinning mechanism 154. The separation area 153 includes a stressconcentrator in the form of a notch, groove, channel or similarstructure that concentrates stress in the separation area 153. Thestress concentrator of the separation area 153 may be notched, scored,indented, pre-weakened or pre-stressed to direct separation of thespinning mechanism 154 from the rotatable shaft 152 under specifictorsional load. The separation area 153 removes the rotatable shaft 152of the mixing element 150 by making a break at a known or predeterminedsite (e.g., a separation area). The separation area may be variouslengths and up to about an inch long. In an embodiment, when torque(twisting) is applied to the mixing element 150, the rotatable shaft 152separates from the spinning mechanism 154. The twisting creates asufficient shear to create a clean separation of the stirrer/shaftinterface. In an embodiment, the spinning mechanism 154 is released fromthe rotatable shaft 152 by use of an active release mechanism. Onceactuated, the active release mechanism will disengage the stirrer fromthe shaft.

In an embodiment, the mixing element 150 includes a rotatable shaft 152configured to vibrate. In an embodiment, the rotatable shaft 152 may bea thin, flexible, wire-like body that vibrates all along the length ofthe rotatable shaft 152. In an embodiment, the rotatable shaft 152 maybe attached to an electric motor for powering the vibration of themixing element 150. The electric motor may include a piezoelectricelement that is able to convert current into an ultrasonic vibration.The frequency of vibration of the mixing element 150 may be selected forthe desired viscosity of the bone cement mixture, and need not be in theultrasonic range. Likewise, the amplitude of the vibrations created bythe mixing element 150 may vary according to the desired viscosity ofthe bone cement mixture. In an embodiment, the desired viscosity of thebone cement mixture may include a controller coupled to the motorwhereby the user may vary the frequency and amplitude of the vibration.

The mixing element 150 is introduced into a side arm of the adapter 115that engages the proximal end 102 of the delivery catheter 110. Themixing element 150 runs through the elongated shaft of the deliverycatheter 110 through the mixing element conduit and up into the proximalend 123 of the expandable body 103, as shown in FIG. 2.

In an embodiment, carbon nanotubes (CNTs) are added to the bone cementto increase the strength of the material. Carbon nanotubes are anallotrope of carbon that take the form of cylindrical carbon moleculesand have novel strength properties. Carbon nanotubes exhibitextraordinary strength. Nanotubes are members of the fullerenestructural family, which also includes buckyballs. Whereas buckyballsare spherical in shape, a nanotube is cylindrical with at least one endtypically capped with a hemisphere of the buckyball structure. Nanotubesare composed entirely of sp2 bonds, similar to those of graphite. Thisbonding structure, which is stronger than the sp3 bonds found indiamond, provides the molecules with their unique strength. Nanotubesnaturally align themselves into “ropes” held together by Van der Waalsforces. Single walled nanotubes or multi-walled nanotubes may be used tostrengthen the reinforcing materials.

In an embodiment, a fracture repair process reinforces a weakened orfractured bone without exposing the bone through a traditional surgicalincision. The presently disclosed embodiments use a minimally invasiveapproach by making a minor incision to gain access to the bone.Minimally invasive refers to surgical means, such as microsurgical,endoscopic or arthroscopic surgical means, that can be accomplished withminimal disruption of the pertinent musculature, for instance, withoutthe need for open access to the tissue injury site or through minimalincisions. Minimally invasive procedures are often accomplished by theuse of visualization such as fiber optic or microscopic visualization,and provide a post-operative recovery time that is substantially lessthan the recovery time that accompanies the corresponding open surgicalapproach. Benefits of minimally invasive procedures include causing lesstrauma because there is minimal blood loss, a reduction in surgery andanesthetized time, shortened hospitalization, and an easier and morerapid recovery. In an embodiment, a bone fixator may be placed within anintramedullary cavity of a weakened or fractured bone. By restoring andpreserving bone structure, some of the presently disclosed embodimentspermit additional future treatment options.

FIG. 5 illustrates close-up views of the distal end 104 of the systemfor repairing a weakened or fractured bone. FIG. 5A-D show exemplarymethod steps in the mixing of the two-component bone cement within theelongated body 103 in situ. FIG. 5A shows an expandable body 103 housinga powder component 122 of a bone cement. The expandable body 103 isattached to the distal end 104 of the delivery catheter 110. The powdercomponent 122 may be pre-loaded in the expandable body 103 or added tothe expandable body 103 by injection, suction, or other methods known inthe art. In FIG. 5B, a liquid component 124 of the two-component bonecement is added to the expandable body 103. Once the powder component122 and the liquid component 124 of the bone cement are together, amixing element 150 terminating in a spinning mechanism 154 is placedthrough an inner lumen of the delivery catheter 110 and positioned withthe expandable body 103, see FIG. 5C. The spinning mechanism 154 isturned on and the powder component 122 and liquid component 124 of thebone cement are mixed together to produce a homogenous cement materialwith a desired viscosity. During mixing of the powder and liquidcomponents of the bone cement, the liquid component should bedistributed equally throughout the mixture so that the mixture isuniform and possesses a uniform viscosity, consistent with themanufacturer's specifications. The mixing of the two-components causesthe expandable body 103 to move from a first compact state to a secondexpanded state. As shown in FIG. 5D, once the bone cement is at adesired viscosity, the mixing element 150 is removed from the deliverycatheter 110. In an embodiment, a vacuum is created so that theproduction of air bubbles is minimized. For example, a vacuum pump maybe attached to the Tuohy-Borst adapter 115 located at the proximal end102 of the delivery catheter 110. After the mixing element 150 isremoved from the delivery catheter 110, the mixed bone cement is able togo through a curing cycle. A pressure sensor/gauge may be incorporatedinto the system for repairing a weakened or fractured bone to assist atreating physician in monitoring the procedure. Alternately, thespinning mechanism 154 of the mixing element 150 may be disengaged fromthe rotatable shaft 152 and remain within the expandable body 103. Themixed bone cement is then cured within the expandable body 103 andaround the spinning mechanism 154. The combination of the expandablebody 103, the hardened bone cement, and the spinning mechanism 154,function as a rebar-enforced IBFD 100.

FIG. 6A and FIG. 6B illustrate close-up views of the distal end 104 ofthe system for repairing a weakened or fractured bone. FIG. 6A shows aninternal bone fixation device (IBFD) 103 in a first compact state beforea liquid component of a bone cement has been added to the IBFD 103. FIG.6B shows the internal bone fixation device (IBFD) 103 in a secondexpanded state after following method steps for repairing a weakened orfractured bone. A minimally invasive incision (not shown) is madethrough the skin of the patient's body to expose a fractured bone 602.The incision may be made at the proximal end or the distal end of thefractured bone 602 to expose the bone surface. Once the bone 602 isexposed, it may be necessary to retract some muscles and tissues thatmay be in view of the bone 602. An access hole 610 is formed in the boneby drilling or other methods known in the art. In an embodiment, theaccess hole 610 has a diameter of about 3 mm to about 10 mm. In anembodiment, the access hole 610 has a diameter of about 3 mm.

The access hole 610 extends through a hard compact outer layer of thebone into the relatively porous inner or cancellous tissue. For boneswith marrow, the medullary material should be cleared from the medullarycavity prior to insertion of the IBFD 103. Marrow is found mainly in theflat bones such as hip bone, breast bone, skull, ribs, vertebrae andshoulder blades, and in the cancellous material at the proximal ends ofthe long bones like the femur and humerus. Once the medullary cavity isreached, the medullary material including air, blood, fluids, fat,marrow, tissue and bone debris should be removed to form a void. Thevoid is defined as a hollowed out space, wherein a first positiondefines the most distal edge of the void with relation to thepenetration point on the bone, and a second position defines the mostproximal edge of the void with relation to the penetration site on thebone. The bone may be hollowed out sufficiently to have the medullarymaterial of the medullary cavity up to the cortical bone removed. Thereare many methods for removing the medullary material that are known inthe art and within the spirit and scope on the presently disclosedembodiments. Methods include those described in U.S. Pat. No. 4,294,251entitled “Method of Suction Lavage,” U.S. Pat. No. 5,554,111 entitled“Bone Cleaning and Drying system,” U.S. Pat. No. 5,707,374 entitled“Apparatus for Preparing the Medullary Cavity,” U.S. Pat. No. 6,478,751entitled “Bone Marrow Aspiration Needle,” and U.S. Pat. No. 6,358,252entitled “Apparatus for Extracting Bone Marrow.”

A guidewire (not shown) may be introduced into the bone 602 via theaccess hole 610 and placed between bone fragments 604 and 606 of thebone 602 to cross the location of a fracture 605. The guidewire may bedelivered into the lumen of the bone 602 and crosses the location of thebreak 605 so that the guidewire spans multiple sections of bonefragments. As shown, the IBFD 103, which is constructed and arranged toaccommodate the guidewire, is delivered over the guidewire to the siteof the fracture 605 and spans the bone fragments 604 and 606 of the bone602. Once the IBFD 103 is in place, the guidewire may be removed. Thelocation of the IBFD 103 may be determined using at least one radiopaquemarker 130 which is detectable from the outside or the inside of thebone 602. For example, as shown in the embodiment depicted in FIG. 6,radiopaque markers 130, which are visible from outside of the body usingx-ray or other detection means, are located along both the IBFD 103 andthe slip sleeve 107 of the delivery catheter 110 to help align andposition the system 100. Once the IBFD 103 is in the correct positionwithin the fractured bone 602, the system 100 is attached to a deliverysystem which contains a bone cement. The delivery system may house bothcomponents of the bone cement, for example the powder component and theliquid component, or just the liquid component. In an embodiment, theIBFD 103 comes pre-loaded with the powder component of the bone cement.The liquid component of the bone cement is then infused through a voidin the delivery catheter 110 and enters the IBFD 103 of the system 100.Once orientation of the bone fragments 604 and 606 are confirmed to bein a desired position, a mixing element terminating in a spinningmechanism is placed through an inner lumen of the delivery catheter andpositioned within the IBFD 103. The spinning mechanism is turned on andthe powder component and liquid component of the bone cement are mixedtogether to produce a homogenous cement material with a desiredviscosity. The mixing of the two-components causes the expandable body103 to move from a first compact state to a second expanded state. Oncethe bone cement is at a desired viscosity, the mixing element is removedfrom the delivery catheter. In an embodiment, a vacuum is created sothat the production of air bubbles is minimized. After the mixingelement is removed from the delivery catheter, the mixed bone cement isable to go through a curing cycle. Once the mixed bone cement has beenhardened within the IBFD 103, the IBFD 103 may be released from thedelivery catheter by known methods in the art. In an embodiment, thedelivery catheter is cut to separate the IBFD 103 from the elongatedshaft. A device slides over the delivery catheter and allows a rightangle scissor to descend through the delivery catheter and make a cut.The location of the cut may be determined by using a fluoroscope or anx-ray. In an embodiment, the cut location is at the junction where theelongated shaft meets the IBFD 103.

In an embodiment, the system 100 is used to treat a hand or wristfracture. The wrist is a collection of many joints and bones that allowuse of the hands. The wrist has to be mobile while providing thestrength for gripping. The wrist is complicated because every small boneforms a joint with its neighbor. The wrist comprises at least eightseparate small bones called the carpal bones, that connect the two bonesof the forearm, called the radius and the ulna, to the bones of the handand fingers. The wrist may be injured in numerous ways. Some injuriesseem to be no more than a simple sprain of the wrist when the injuryoccurs, but problems can develop years later. A hand fracture may occurwhen one of the small bones of the hand breaks. The hand consists ofabout 38 bones and any one of these bones may suffer a break. The palmor midhand is made up of the metacarpal bones. The metacarpal bones havemuscular attachments and bridge the wrist to the individual fingers.These bones frequently are injured with direct trauma such as a crushfrom an object or most commonly the sudden stop of the hand by a wall.The joints are covered with articular cartilage that cushions thejoints. Those skilled in the art will recognize that the discloseddevice and methods can be used for to treat fractures to other bones,such as radius, ulna, clavicle, metacarpals, phalanx, metatarsals,phalanges, tibia, fibula, humerus, spine, ribs, vertebrae, and otherbones and still be within the scope and spirit of the disclosedembodiments.

The presently disclosed embodiments may be used to treat a claviclefracture, resulting in a clavicle reduction. The clavicle or collar boneis classified as a long bone that makes up part of the shoulder girdle(pectoral girdle). Present methods to affix a broken clavicle arelimited. The clavicle is located just below the surface of the skin, sothe potential for external fixation including plates and screws islimited. In addition, the lung and the subclavian artery reside belowthe collar bone so using screws is not an attractive option. Traditionaltreatment of clavicle fractures is to align the broken bone by puttingit in place, provide a sling for the arm and shoulder and pain relief,and to allow the bone to heal itself, monitoring progress with X-raysevery week or few weeks. There is no fixation, and the bone segmentsrejoin as callous formation and bone growth bring the fractured bonesegments together. During healing there is much motion at the fractureunion because there is not solid union and the callous formation oftenforms a discontinuity at the fracture site. A discontinuity in thecollar bone shape often results from a clavicle fracture.

The presently disclosed embodiments and methods treat a claviclefracture in a minimally invasive manner and may be used for a claviclereduction or collar bone reduction. A benefit of using the discloseddevice to repair a collar bone is the repair minimizes post repairmisalignment of collar bone. A benefit of using the disclosed device torepair a clavicle is to resolve the patient's pain during the healingprocess.

A method for repairing a fractured bone includes gaining access to aninner cavity of the fractured bone; providing a system for use inrepairing the fractured bone, the system comprising an internal bonefixation device releasably engaging a delivery catheter, the internalbone fixation device housing a powder component of a bone cement;positioning the internal bone fixation device spanning at least two bonesegments of the fractured bone; adding a liquid component of the bonecement to the internal bone fixation device by passage through an innervoid of the device; inserting the mixing element through the deliverycatheter and into the internal bone fixation device; activating themixing element to mix the powder component and the liquid component ofthe bone cement within the internal bone fixation device, wherein theinternal bone fixation device moves from a first compact state to asecond expanded state; removing the mixing element from the device;waiting for the mixed bone cement to cure, wherein the curing of thebone cement results in a hardened internal bone fixation device; andreleasing the hardened internal bone fixation device from the deliverycatheter.

A method for repairing a fractured bone includes gaining access to aninner cavity of the fractured bone; providing a system for use inrepairing the fractured bone, the system comprising an internal bonefixation device releasably engaging a delivery catheter, the internalbone fixation device housing a powder component of a bone cement;positioning the internal bone fixation device spanning at least two bonesegments of the fractured bone; adding a liquid component of the bonecement to the internal bone fixation device by passage through an innervoid of the device; inserting a mixing element through the deliverycatheter and into the internal bone fixation device, the mixing elementcomprising a spinning mechanism releasably engaging a rotatable shaft;activating the mixing element to mix the powder component and the liquidcomponent of the bone cement within the internal bone fixation device,wherein the internal bone fixation device moves from a first compactstate to a second expanded state; releasing the spinning mechanism fromthe rotatable shaft; removing the rotatable shaft from the device;waiting for the mixed bone cement to cure, wherein the curing of thebone cement results in a hardened rebar-enforced internal bone fixationdevice; and releasing the hardened rebar-enforced internal bone fixationdevice from the delivery catheter.

All patents, patent applications, and published references cited hereinare hereby incorporated by reference in their entirety. It will beappreciated that several of the above-disclosed and other features andfunctions, or alternatives thereof, may be desirably combined into manyother different systems or applications. Various presently unforeseen orunanticipated alternatives, modifications, variations, or improvementstherein may be subsequently made by those skilled in the art which arealso intended to be encompassed by the following claims.

1. A system for repairing a fractured long bone comprising: a deliverycatheter having an elongated shaft with a proximal end, a distal end,and a longitudinal axis therebetween, wherein the delivery catheter hasan inner void for passage of one or more bone cement components and aninner lumen; an internal bone fixation device releasably engaging thedistal end of the delivery catheter, the internal bone fixation devicemoveable from a first compact state to a second expanded state; arotatable shaft, wherein the rotatable shaft is sized to pass throughthe inner lumen of the delivery catheter; and a spinning mechanism,wherein the spinning mechanism extends from the rotatable shaft, andwherein the spinning mechanism is sized to pass through the inner lumenof the delivery catheter and into the internal bone fixation device,wherein, when the internal bone fixation device is positioned within acavity of the fractured long bone, and the one or more bone cementcomponents are positioned in the internal bone fixation device, the oneor more bone cement components are mixeable to a desired viscosity byactivating the spinning mechanism within the internal bone fixationdevice.
 2. The system of claim 1 further comprising an adapterreleasably engaging the proximal end of the delivery catheter, wherein afirst side-arm of the adapter receives the spinning mechanism and asecond side-arm of the adapter receives a bone cement injection systemhousing the one or more bone cement components.
 3. The system of claim 1wherein the internal bone fixation device is shaped as an elongatedcylinder.
 4. The system of claim 1 wherein the one or more bone cementcomponents include a powder component and a liquid component.
 5. Thesystem of claim 4 wherein the powder component is polymethylmethacrylatepowder and the liquid component is methyl methacrylate.
 6. The system ofclaim 1 further comprising a handle, wherein the handle engages a drivemechanism for rotating the rotatable shaft.
 7. The system of claim 6wherein rotating the rotatable shaft about a central axis rotates thespinning mechanism about the central axis.
 8. The system of claim 1wherein, when the internal bone fixation device resides within thecavity of the fractured long bone, the internal bone fixation devicespans at least two long bone fragments and provides support to the atleast two long bone fragments.
 9. The system of claim 8 wherein theinternal bone fixation device evenly contacts a wall of the cavity ofthe at least two long bone fragments when in the second expanded state.10. The system of claim 1 wherein a stress concentrator is disposedbetween the internal bone fixation device and the distal end of thedelivery catheter to facilitate release of the internal bone fixationdevice from the delivery catheter.
 11. The system of claim 1 wherein thespinning mechanism is releasably engaged to a distal end of therotatable shaft.
 12. A method for repairing a fractured bone comprising:gaining access to an inner cavity of the fractured bone; providing asystem for use in repairing the fractured bone, the system comprising aninternal bone fixation device releasably engaging a delivery catheter,the internal bone fixation device housing a powder component of a bonecement; positioning the internal bone fixation device spanning at leasttwo bone segments of the fractured bone; adding a liquid component ofthe bone cement to the internal bone fixation device by passage throughan inner void of the device; inserting a mixing element through thedelivery catheter and into the internal bone fixation device; activatingthe mixing element to mix the powder component and the liquid componentof the bone cement within the internal bone fixation device, wherein theinternal bone fixation device moves from a first compact state to asecond expanded state; removing the mixing element from the device;waiting for the mixed bone cement to cure, wherein the curing of thebone cement results in a hardened internal bone fixation device; andreleasing the hardened internal bone fixation device from the deliverycatheter.
 13. The method of claim 12 wherein the hardened internal bonefixation device remains in the inner cavity of the fractured bone tosupport the fractured bone.
 14. The method of claim 12 wherein thedelivery catheter further comprises: a stiffening member surrounding anelongated shaft of the delivery catheter; a slip sleeve surrounding thestiffening member; and at least one radiopaque material on the deliverycatheter.
 15. The method of claim 12 wherein the mixing elementcomprises a rotatable shaft engaging a spinning mechanism at a distalend, wherein rotating the rotatable shaft causes the spinning mechanismto spin and mix together the bone cement components within the internalbone fixation device.
 16. The method of claim 12 wherein the powdercomponent is polymethylmethacrylate powder and the liquid component ismethyl methacrylate.
 17. A method for repairing a fractured bonecomprising: gaining access to an inner cavity of the fractured bone;providing a system for use in repairing the fractured bone, the systemcomprising an internal bone fixation device releasably engaging adelivery catheter, the internal bone fixation device housing a powdercomponent of a bone cement; positioning the internal bone fixationdevice spanning at least two bone segments of the fractured bone; addinga liquid component of the bone cement to the internal bone fixationdevice by passage through an inner void of the device; inserting amixing element through the delivery catheter and into the internal bonefixation device, the mixing element comprising a spinning mechanismreleasably engaging a rotatable shaft; activating the mixing element tomix the powder component and the liquid component of the bone cementwithin the internal bone fixation device, wherein the internal bonefixation device moves from a first compact state to a second expandedstate; releasing the spinning mechanism from the rotatable shaft;removing the rotatable shaft from the device; waiting for the mixed bonecement to cure, wherein the curing of the bone cement results in ahardened rebar-enforced internal bone fixation device; and releasing thehardened rebar-enforced internal bone fixation device from the deliverycatheter.
 18. The method of claim 17 wherein the hardened rebar-enforcedinternal bone fixation device remains in the inner cavity of thefractured bone to support the fractured bone.
 19. The method of claim 17wherein rotating the rotatable shaft causes the spinning mechanism tospin and mix together the bone cement components within the internalbone fixation device.
 20. The method of claim 17 wherein the powdercomponent is polymethylmethacrylate powder and the liquid component ismethyl methacrylate.